In recent years, the demand for lead free in a piezoelectric material is increasing, and thus the study is rising on potassium sodium niobate [(K, Na)NbO3 (hereinafter also referred to as KNN)]. The KNN attracts a lot of attentions because it has a relatively high curie temperature and good piezoelectric properties despite the fact that it is a lead-free piezoelectric material.
With respect to the utilization of the piezoelectric material, the practicality of a film piezoelectric material is developing in place of a bulk piezoelectric material. As an example of the use of such a material, a gyro sensor and a shock sensor or the like where the piezoelectric effect is involved that the force applied to the piezoelectric layer is converted into a voltage, and an actuator, an ink jet head, a loudspeaker, a buzzer, a resonator and the like where the inverse piezoelectric effect is involved that the piezoelectric layer will be deformed when a voltage is applied.
If the piezoelectric material is made as a film, the component may be downsized and can be used in more fields. In addition, as a plurality of components can be prepared in a substrate in a lump, the productivity is increased. Further, there are lots of advantages in terms of performance such as the enhancement of the sensitivity when the piezoelectric material is prepared to be a sensor.
As the indexes for the use of the piezoelectric material, d31 or e31 which is the piezoelectric constant can be listed. The larger the absolute value is, the better the piezoelectric effect and inverse piezoelectric effect will be.
Among the existing piezoelectric materials, most contain lead such as the representative lead zirconate titanate (PZT). From the viewpoint of environment, a piezoelectric material free of lead is demanded to be developed.